Credit for photovoltaic system with storage: Your guide to optimal financing in 2025
27 Jun 2025
3
Minutes
Katrin Straub
CEO at nextsure
The purchase of a photovoltaic system with storage is a significant investment in your energy independence. But how can a project of over 20,000 euros be best financed? This article guides you through the process, from choosing the right loan to securing your system.
The topic in brief and concise terms
A loan for a photovoltaic system with storage costs around €25,000 for a 10-kWp system, with subsidised loans (KfW 270) often offering the most favourable interest rates.
Alongside the loan, insurance (all-risk, liability, storage) is crucial to secure the investment and financing.
Be sure to check out regional funding programmes that can be combined with bank loans and can reduce the total costs by several hundred euros.
Market Overview: Costs and Financing Options at a Glance
An average photovoltaic system with a ten kilowatt-peak (kWp) capacity and suitable storage will cost around 25,000 euros in 2025. For financing, you generally have three options: the KfW promotional loan, special solar loans from banks, or a traditional installment loan. Interest rates for promotional loans like the KfW Programme 270 are often around 4.6 percent. Thanks to the guaranteed feed-in tariff and savings on electricity costs, the system partly pays for itself. The payback period is typically between ten and 15 years, depending on your own consumption. A solar loan for your system is often available without a land registry entry for amounts up to 50,000 euros. These figures form the basis for your financing decision.
Practical Example: How the Financing for a Detached House Works Out
The Situation: The Schmidt Family Plans for the Future
The Schmidt family consumes 4,500 kilowatt-hours of electricity annually and wishes to become more independent. They are planning to purchase a 10-kWp system with a 10-kWh storage unit for 25,000 euros. As they intend to use their equity elsewhere, they opt for full financing. The choice of the right loan can make a difference of several thousand euros over the term.
The Loan Comparison: KfW Loan Versus Bank Loan
A conventional installment loan is offered at 5.5 percent interest, while the Eco-loan with Interest Advantage from KfW costs only 4.6 percent. Over a ten-year term, the Schmidt family saves over 1,200 euros in interest costs just due to the lower interest rate. Regional grants of up to 1,000 euros can further reduce the loan amount. The path to securing the loan follows clear steps.
Obtaining at least three quotes from craftsmen.
Checking regional funding pots before application submission.
Submitting the loan application to the local bank (also for KfW loans).
The bank's review of the loan documents.
Disbursement of the loan after contract signing.
With the right financing in place, the legal and subsidy-related details become the focus.
Expert knowledge: grants, taxes, and legal frameworks
The KfW Programme 270 in Detail
The KfW Programme "Renewable Energies – Standard (270)" is the classic for financing. It supports the installation, expansion, and acquisition of photovoltaic systems, including the associated storage. Loan amounts of up to 100,000 euros are possible, with terms of up to 20 years. Our expert tip: Check with your local council for local subsidies, which can often be combined with the KfW loan. In Cologne, for example, grants of up to 2,500 euros are available.
Tax Aspects of the Loan
If you operate your system as a business with the intention of making a profit, you can claim the loan interest as business expenses for tax purposes. This reduces your tax burden and improves the overall return. In return, the income from the feed-in tariff must be taxed. Careful planning, possibly in combination with financing a roof renovation, is crucial here. Securing this significant investment is the next logical step.
Protecting Your Investment: These Insurances Are Essential
A loan for the acquisition of a photovoltaic system with storage also means a liability to the bank. Lenders often require proof of adequate insurance coverage. A lack of insurance can endanger not only the system but also your financing in the event of damage. Although the lifespan of solar modules is up to 30 years, risks such as severe weather or technical defects remain. Comprehensive protection consists of several components.
Photovoltaic All-Risk Insurance: It covers damage caused by hail, storms, short circuits, or animal bites. The annual costs are around 80 to 120 euros. A good Photovoltaic All-Risk Insurance is fundamental.
Operator Liability Insurance: If a module comes loose from the roof and causes damage, this insurance protects you. Check whether your personal liability insurance covers this or if a separate policy is necessary.
Battery Storage Insurance: The storage is an expensive component with its own technology. A special Battery Storage Insurance covers risks such as deep discharge or electronic damage.
Once financing and insurance are arranged, it is important to avoid long-term mistakes.
Long-term Planning: Avoid Common Mistakes in Financing
The excitement about the new solar system can quickly be dampened by unforeseen costs. Proactive planning can prevent the most common pitfalls. Many underestimate the annual operating costs, which amount to about one percent of the investment sum. You should include this in your profitability calculation from the start. Another aspect is the correct sizing of the installation. An undersized system doesn't maximise your savings potential, while an oversized one has a slower payback period.
Pay attention to these points to ensure long-term success:
Compare quotes: Obtain at least three detailed offers from different specialist companies.
Plan for additional costs: Costs for meter changes (up to 200 euros) or registration with the grid operator are often overlooked.
Review maintenance contract: A maintenance contract secures the yield but should be reasonably priced.
Flexibility with credit: Look for the option of special repayments to pay off the loan faster if financially feasible.
A well-thought-out, long-term strategy, similar to a building savings contract for future renovations, secures the value of your investment.
Request your individual risk analysis now: Have your insurance situation checked free of charge and receive specific optimisation suggestions.
More useful links
KfW provides information on the promotion of photovoltaic systems as part of energy-efficient refurbishment of existing properties.
Federal Network Agency offers statistics on renewable energies, including photovoltaics.
HTW Berlin publishes the 2024 Electricity Storage Inspection, a study of electricity storage systems in connection with photovoltaic systems.
Fraunhofer ISE provides a study on the expansion of photovoltaics and battery storage systems in Germany.
Wikipedia offers a comprehensive article on photovoltaics, their fundamentals, technology, and applications.
BMWK (Federal Ministry for Economic Affairs and Climate Action) presents the 2023 Photovoltaic Strategy.
Consumer Advice Centre offers essential information on planning a solar system (photovoltaic).
dena (German Energy Agency) provides information about the development of building-integrated photovoltaics in Germany.
Federal Association of the Solar Industry (BSW) publishes current market data on the solar industry.
Wikipedia offers an article on the Renewable Energy Sources Act (EEG).
FAQ
How much does a loan for a photovoltaic system with storage cost?
The cost depends on the interest rate and the term. For a loan amount of 20,000 euros with an effective annual interest rate of 4.89 percent over six years, the interest costs amount to approximately 3,000 euros, for example.
What documents do I need for the loan application?
You will generally need the installer’s quote, a profitability calculation, proof of income for the last three months, and a copy of your identity card.
How long does it take to get approval for a solar loan?
After submitting all documents, the review and approval process takes between three and seven business days at most banks.
Is a special repayment possible with the photovoltaic loan?
Yes, most solar and eco loans allow free additional payments or even early full repayment, which further reduces the interest burden.
What happens to the loan if I sell my house?
The loan is generally paid off from the proceeds of the sale. Alternatively, the new owner can take over the loan agreement after a credit check, which can increase the property's value.
What is the lifespan of the system components?
Solar modules have a lifespan of 20 to 30 years. The inverter often needs to be replaced after 10 to 15 years, while a power storage unit lasts around 10 years.
